Method of making a tire using a high crown uni-stage tire building drum

ABSTRACT

A tire building drum and a method of building a tire carcass is disclosed. The tire building drum has a center section comprised of a plurality of segments that are radially and axially movable. The building drum further comprises shoulder sections that are axially movable. The shoulder sections include radially expandable bead locks. The method employs the steps of applying one or more carcass layers, locking the bead locks and moving the center section radially outwardly while moving the bead locks axially inwardly.

FIELD OF THE INVENTION

The invention relates to a tire building drum, more particularly to atire building drum having a high central crown region.

BACKGROUND OF THE INVENTION

The manufacture of tires typically involves a tire building drum whereinnumerous tire components are applied to the drum in sequence, forming acylindrical shaped tire carcass. This stage of the tire building processis commonly referred to as the “first stage” of the tire buildingprocess. The tire carcass is then typically removed from the tirebuilding drum and sent to a second stage, expandable tire shaping drumwhere the carcass is expanded into a toroidal shape for receipt of theremaining components of the tire such as the belt package and a rubbertread. The completed toroidally shape unvulcanized tire carcass or greentire is then removed from the second stage drum and subsequently moldedand vulcanized into a finished tire.

The prior art process thus requires two tire building drums and thetransfer of the carcass from one drum to the other. Further, a problemoften arises in precisely locating and anchoring the tire beads on theunvulcanized tire carcass, especially during the transportation of thetire beads from the first stage drum to the second stage drum.Variations in bead positioning can result in ply distortion in the tire.

Tire manufacturers have recently begun moving towards the utilization ofa single tire building drum, for both the first and second stage tirebuilding. This requires that the tire building drum be capable of axialexpansion and contraction as well as radial expansion/contraction.Further, it is important to maintain a positive bead lock during theentire tire building process, including the tire shaping, so that theply cord length is maintained, resulting in good tire uniformity. Due tothe fact that the tire building drum axially and radially expands, it isimportant that both sides of the tire building drum move insynchronization. If one side of the drum is out of synchronization withthe other side of the drum, problems in tire uniformity can occur. It isadditionally desired to support the apex and bead assembly in a verticalmanner while avoiding unwanted displacements of the tire components,particularly the ply.

SUMMARY OF THE INVENTION

The invention provides in a first aspect a method of building a tirecarcass on a tire building drum. The steps include applying one or moretire building components onto a drum to form a cylindrically shapedunvulcanized tire carcass having carcass ends; placing a first andsecond bead around the tire building components on the drum so that thecarcass ends of the tire carcass extend laterally between the beads;radially expanding a first and second bead lock mechanism intoengagement with a first and second bead; moving the carcass locatedbetween the bead locks radially outward by radially expanding a centerportion of the tire building drum while moving the pair of bead lockmechanisms axially inward.

The invention provides in a second aspect a method of building a tirecarcass on a tire building drum comprising the steps of: applying one ormore tire building components onto a drum to form a cylindrically shapedunvulcanized tire carcass having carcass ends; placing a first andsecond bead around the tire building components on the drum so that thecarcass ends of the tire carcass extend laterally between the beads;radially expanding a first and second bead lock mechanism intoengagement with a first and second bead; expanding the carcass locatedbetween the bead locks radially outward by radially expanding a centerportion of the tire building drum while maintaining the axial tension ofthe carcass located between the bead locks.

DEFINITIONS

For ease of understanding this disclosure, the following items aredefined:

“Apex” means an elastomeric filler located radially above the bead andinterposed between the plies and the ply turn-up.

“Axial” and “axially” means the lines or directions that are parallel oraligned with the longitudinal axis of rotation of the tire buildingdrum.

“Bead” means that part of the tire comprising an annular tensile membercommonly referred to as a “bead core” wrapped by ply cords and shaped,with or without other reinforcement elements such as flippers, chippers,apexes, toe guards and chafers, to fit the design rim.

“Belt Structure” or “Reinforcing Belts” means at least two annularlayers or plies of parallel cords, woven or unwoven, underlying thetread, unanchored to the bead, and having both left and right cordangles in the range from 17° to 27° with respect to the equatorial planeof the tire.

“Carcass” means an unvulcanized laminate of tire ply material and othertire components cut to length suitable for splicing, or already spliced,into a cylindrical or toroidal shape. Additional components may be addedto the carcass prior to its being vulcanized to create the molded tire.

“Casing” means the tire carcass and associated tire components excludingthe tread.

“Chafers” refers to narrow strips of material placed around the outsideof the bead to protect cord plies from the rim, distribute flexing abovethe rim, and to seal the tire.

“Circumferential” means lines or directions extending along theperimeter of the surface of the annular tread perpendicular to the axialdirection.

“Cord” means one of the reinforcement strands of which the plies in thetire are comprised.

“Equatorial Plane (EP)” means the plane perpendicular to the tire's axisof rotation and passing through the center of its tread.

“Innerliner” means the layer or layers of elastomer or other materialthat form the inside surface of a tubeless tire and that contain theinflating fluid within the tire.

“Insert” means an elastomeric member used as a stiffening member usuallylocated in the sidewall region of the tire.

“Ply” means a continuous layer of rubber-coated parallel cords.

“Radial” and “radially” mean directions radially toward or away from theaxis of rotation of the tire building drum.

“Radial Ply Tire” means a belted or circumferentially restrictedpneumatic tire in which at least one layer of ply has the ply cordsextend from bead to bead at cord angles between 65° and 90° with respectto the equatorial plane of the tire.

“Shoulder” means the upper portion of sidewall just below the treadedge.

“Sidewall” means that portion of a tire between the tread and the bead.

“Tread” means a rubber component which when bonded to a tire carcassincludes that portion of the tire that come into contact with the roadwhen the tire is normally inflated and under normal load.

“Tread Width” means the arc length of the tread surface in the axialdirection, that is, in a plane parallel to the axis of rotation of thetire.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described by way of example and with reference tothe accompanying drawings in which:

FIGS. 1A and 1B are perspective side views of a tire building drum shownin the start position and the high crown (radially expanded) position;

FIG. 2 is a cross-sectional view of the tire building drum shown in thestart position;

FIG. 3 is a cross-sectional view of the tire building drum shown in thebead lock position;

FIG. 4 is a cross-sectional view of the tire building drum in theexpanded high crown condition;

FIG. 5 is a cross sectional view of the tire building drum showing thestop pin locked in the outside position;

FIG. 6 is an end view of the tire building drum taken in the direction6-6 of FIG. 5 showing the lock ring in the locked position;

FIG. 7 is a cross sectional view of the tire building drum showing thestop pin unlocked;

FIG. 8 is an end view of the tire building drum taken in the direction8-8 of FIG. 7 showing the lock ring in the unlocked position;

FIG. 9 is a cross sectional view of the tire building drum showing thestop pin locked in the inside position preventing shoulder axialmovement;

FIG. 10 is an end view of the tire building drum taken in the direction10-10 of FIG. 9 showing the lock ring locking the stop pins in theinside position;

FIG. 11 is a cross sectional view of the tire building drum shown in thedrum shaping position;

FIG. 12 is a perspective view of a synchronization mechanism for thetire building drum;

FIGS. 13A and 13B are cross sectional views of the tire building drumshowing the center synchronization member and the center segment in thecollapsed position and in the radially expanded position, respectively;

FIGS. 14A and 14B are top, side views of the center segments shown inthe axially collapsed position and the axially expanded position,respectively;

FIGS. 15 and 16 are cutaway perspective views of the tire building drumwith the center segments removed, and showing the center synchronizationmechanism and the lifter arms in the retracted and the radially outerposition, respectively.

DETAILED DESCRIPTION OF THE INVENTION

With reference to FIGS. 1 through 5, an exemplary tire building drum 5of the present invention is illustrated. As shown more particularly inFIGS. 1A and 1B, the tire building drum 5 has a left hand side 7 and aright hand side 9 joined together by a center section 20. The centersection is further divided into a right hand side and a left hand side,which are both axially and radially movable, as described in moredetail, below. Adjacent the center section 20 are first and second beadlocking mechanisms 25, which are also radially movable as shown in FIG.1B. Adjacent the bead locking mechanisms are first and second shouldersegments 29. Both the bead locking mechanisms and the shoulder segmentsare axially movable. Thus, both the left hand side and the right handside of the drum are axially movable. These components are described inmore detail, below.

Center Section

The center section 20 of the tire building drum further comprises aplurality of center segments 22 located about the outer circumference ofthe drum. Each of the center segments are split into a left hand side 22a and a right hand side 22 b, as shown in FIG. 14. Each side 22 a, 22 bhas one or more finger-like projections 24 which are slidably receivedin one or more opposed recesses 26 in an interdigitated or interlockedmanner. The center segments 22 can thus axially expand or contract asthe fingers slide within the recesses.

The center section 20 may also radially expand as shown in FIGS. 1 b and4. The center section 20 can radially expand in the range of about 20 toabout 50 mm. As each center segment 22 radially expands, the gap betweencenter segments increases. Provided within each center segment half 22a,b is a radially oriented piston chamber 28. Received in each chamber28 is an elbow-shaped linkage 30 connected to an actuator 32, such as apiston 33. A control system (not shown) actuates the pistons 33, causinglinkage 30 to slide from the retracted position shown in FIG. 3 to theactuated position shown in FIG. 4. When the linkages 30 are actuated,the linkages push the center segments radially outward into the highcrown position as shown in FIG. 4.

In order to ensure that the left hand side and right hand side of thecenter segments 22 move together in synchronization, a centersynchronization mechanism 50 is provided, and is shown in FIG. 12. Thecenter mechanism 50 includes two outer rings 52 joined together by afirst and second linkage mechanism 54. The rings 52 are rotatablymounted in the tire building drum within the center segments 22. Thelinkage mechanisms 54 function to keep the outer rings 52 rotating insynchronization together. When linkages 30 are actuated to push thecenter section into the high crown position, the linkages 30 push up aplurality of lifter rods 35 through slots 37. The lifter rods 35 areconnected to a plurality of support arms 39 which are connected to theouter rings 52. When the lifter rods 35 are actuated into their radiallyouter position, the support arms 39 are likewise actuated into theirradially outer position, causing both of the center rings 52 to rotate.The connecting linkage 54 between the center rings 52 keeps the ringsrotating in synchronization so that the left hand side and the righthand side of the center segments 22 a,b move together when actuated inthe radial direction. See FIGS. 13 a and 13 b and FIGS. 15-16.

The first and second linkage mechanisms 54 also allow the outer rings 52to axially expand and contract. The linkages of the linkage mechanism 54can fold up as shown in FIG. 9, enabling the center section of the tirebuilding drum to have an axially smaller dimension. The linkages 54 mayalso outwardly expand, enabling the center section of the tire buildingdrum to have an axially wider position. FIG. 4 illustrates the linkagesin a partially expanded condition.

The exterior surface of the center section is covered by a sleeve 60mounted thereon. Each end 62 of the sleeve 60 are secured in sleeveclamps 70 located adjacent the center section segments. The sleeveclamps 70 move axially inward during the center radial expansion intothe high crown position, retarding motion of the center sleeve. Thisfeature prevents the tire components from moving since the underlyingsleeve does not move, resulting in better tire uniformity. The sleeveclamps 70 are actuated by pistons 72 controlled by the tire drum control(not shown). When the center section of the tire building drum isexpanded radially outward into the high crown position, the sleeve clamppistons 72 are actuated, resulting in the sleeve clamps 70 slidingaxially into a recess 74 located between the bead lock mechanism and thecenter segments. This motion is coordinated in order to retard motion ofthe sleeve. Thus, the axial tension of the sleeve is maintained due tothe actuation of the bead locks, as well as the ply and other tirecomponents. However, the circumferential tension in the sleeve is higherover the high crown section. When the drum screws axially togetherduring the shaping of the tire, the sleeve is no longer axiallytensioned, and buckles up over the center section as shown in FIG. 11.

Bead Lock Mechanism

Adjacent the center section 20 are first and second annular bead lockingmechanisms 25. FIG. 2 illustrates the bead locking mechanisms 25 in theretracted position, while FIG. 3 illustrates the bead locking mechanisms25 in the radially expanded or bead clamp position. The drum controlsystem (not shown) actuates the bead lock pistons 27 into engagementwith rocker arm 29 which engages an end of the bead lock mechanism,pushing the bead lock mechanism radially outward into the bead clampposition.

The bead lock mechanisms are also independently axially movable, asdescribed below. Further, the amount of axial movement of the bead lockmechanisms may be adjusted by the positioning of stop pin 85 shown inFIGS. 5 and 6.

Shoulder Section and Shoulder Clamp Lock

The right and left hand shoulder section 29 of the tire building drum 5is defined as the drum components located axially outward of thecenterline of the center section, inclusive of the sleeve clamps and thebead lock mechanisms. The left and right hand shoulder sections of thetire building drum are axially slidable on bearing sleeves. The shouldersections 29 are actuated by drive pins 125 mounted on nuts 130, whichride along drive screw 121. When the central screw is rotated, the nuts130 move axially inward/outward, causing the drive pins 125 and eachshoulder section to move axially inward/outward in correspondingfashion. In addition, the drive pins are also in mechanical cooperationwith the split center segments, causing the split center segments 22 a,bto axially extend or contract.

When the center section 20 of the tire building drum 5 moves into thehigh crown position as shown in FIG. 4, the bead lock mechanisms 25 andthe sleeve clamp mechanism 70 are further actuated axially inward bypistons 72,73 so that sleeve clamp is received in recess 74. The beadlock mechanisms and the sleeve clamps are actuated axially inward aboutthe same axial distance as the radial distance traveled by the centersegments 22 into the high crown position. The axial actuation of thebead lock mechanisms and sleeve clamps preferably occurs simultaneouslywith the movement of the center segments into the high crown position.

Because both shoulder sections 29 can move axially, it is important tosecure the shoulder sections in place after the center section 25 of thetire drum has moved into the high crown position. In order to secureeach shoulder section, a rotatable lock ring 80 mounted in each sectionof the shoulder section, locks one or more stop pins 85 in its outerposition. When the stop pin is in its outer position, the shouldersection can move axially. See FIGS. 5 and 6. One or more actuators suchas an air piston 92 actuate the rotatable lock ring 80. When theshoulder section is actuated to its axially inner position, stop pin 85is also actuated or locked in its inner position as shown in FIGS. 9 and10. Lock ring is rotated over the retracted stop pin openings,preventing the stop pin from moving. Since the stop pin cannot move, theshoulder sections which are engaged by the stop pin, are prevented fromaxially moving as well.

Drive Shaft

A central drive shaft 120 is provided for rotational movement of thetire building drum 5 about its longitudinal axis. The central shaft 120is connected to a drive means (not shown). Provided within the centraldrive shaft 120 is a central screw 121. The central screw 121 issupported at each end by bearings 123. The threads on one side of thecentral screw 121 are left handed and on the opposite side are righthanded. On the left hand side is an inboard nut 125 connected to the oneend of the threaded screw 121 and similarly on the opposite right handside is an outboard ball nut 125 connected to the central screw 121.

Turn Up Bladders

An upper bladder 150 extends axially outward from the bead lockmechanism 25 to the respective ends of the tire building drum. The upperbladder 150 extends over a lower bladder 152, which is mounted in theshoulder area of the drum and extends axially outward to the respectiveends of the tire building drum. The upper and lower bladders function asturnup bladders which are used to inflate and, thereby, make the turn-upends of the ply wrap about the apex and bead cores.

Method of Operation

The sequence of building an exemplary tire utilizing the tire drum ofthe present invention is explained below. The tire building can be fullyautomated or may require an operator to manually cut and splice thecomponents as they are applied to the tire building drum 5. Thecomponents listed below can be varied for a particular tireconstruction. Some tires have more components than others. For example,some tires of the tube type may not require a liner.

First, the drum is set to the start position, as shown in FIGS. 1 a and1 b. In the start position, the center section and shoulder sections arein their radially innermost positions, and the drum width is set to thestart position. The start position width may very depending on the tirebeing manufactured. Next, the tire building components such as the tireliner, shoulder gum strips, chafers, sidewalls, optional run flatinserts, and ply are applied to the drum in successive order.

Each of the components described above requires, if applied separately,a rotation of the building drum 5 to form the component into acylindrical shape. Alternatively, these components may be fed to thetire building drum 5 as one or more subassemblies. In either case, theends of the components or subassemblies must be spliced together.

Next, the bead cores are positioned axially at a predetermined axiallocation generally above or slightly inward of the chafers but over thetoe guard strip if used. Then, an apex filler strip would be placed withan end onto bead core and extending axially inwardly relative to thebead cores. Alternatively, the use of a preassembled bead-apexsubassembly can be used. It is important to note that the tire buildingdrum of the present invention can utilize beads of different diametersfor the same tire.

The bead-apex subassembly is then pivoted into axially alignment withthe axis of the tire building drum 5. Similarly, the bead loaders arepositioned into axial alignment with the tire building drum 5. Oncealigned, the bead loaders move axially inwardly over the bead core toposition the bead-apex subassemblies 2 precisely onto thecylindrically-shaped carcass 10 over the bead lock mechanism of the tirebuilding drum. The bead loader then releases the bead apex subassemblyon the drum 5 while the drum bead lock mechanism radially expands,locking the bead cores into position. The bead lock mechanisms areactuated by the bead lock pistons 27, which contact rocker arm 29,pushing the bead lock mechanism radially outward into engagement withthe bead or bead apex subassembly.

Next, the center of the drum expands into the high crown position as theshoulder segments move axially inward. The drum control system (notshown) actuates pistons 33, causing the linkages 30 to slide from theretracted position shown in FIG. 3 to the actuated position shown inFIG. 4. When the linkages 30 are actuated, the linkages push the centersegments radially outward into the high crown position as shown in FIG.4. When linkages 30 are actuated to push the center section into thehigh crown position, the linkages 30 push up a plurality of lifter rods35 through slots 37. The lifter rods 35 are connected to a plurality ofsupport arms 39 which are connected to the outer rings 52. When thelifter rods 35 are actuated into their radially outer position, thesupport arms 39 are likewise actuated into their radially outerposition, causing both of the center rings 52 to rotate in the samedirection. The connecting linkage 54 between the center rings 52 keepsthe rings rotating in synchronization so that the left hand side and theright hand side of the center segments move together when actuated inthe radial direction. See FIGS. 11 a and 11 b and FIGS. 13-14.

When the center of the drum expands into high crown position, the rightand left hand shoulder sections move axially inwards until the sleeveclamps abut the crown pistons 28. Then the shoulder sections are lockedinto place when lock ring rotated by air pistons, entrapping the lockpins in their innermost position, preventing the shoulder sections fromaxially moving.

Next, the ply turnup ends can be folded over by actuating the inflatableturnup bladders at each inboard and outboard end of the building drum 5.The turnup bladders roll the carcass ply turnups and the sidewalls, ifthey have been previously attached, over onto the central supportsegments and carcass ply. As noted, the center segments radiallytypically expand approximately 30 millimeters above the initial startposition. However, the amount of radial expansion may vary dependingupon the tire size. It is desired to have a range of expansion fromabout 20 mm to about 50 mm. This permits the triangular shaped apex tobe folded over at the tip or radial extremes, however, maintaining itsvertical position or almost vertical position relative to the thickestor base portions of the apex nearest the bead cores 12. This greatlyfacilitates the construction of the carcass ply and ensures that theapexes are not overly distorted during the building process as iscommonly done in the prior art method of assembling tire carcasses.

Once the tire turnup ends are folded over, the sidewalls can then eitherbe applied or if previously applied, the entire assembly can then bestitched using roller mechanisms (not shown). The stitching procedureensures that entrapped air is pushed outwardly of the carcass and thatthe components are firmly adhered to the adjacent underlying tirecarcass components.

Once the stitching has been accomplished, the tire building drum axiallycontracts. The building drum 5 between the beads is charged with air orother fluid medium which passes through the central segment supportmechanism and the radially expanded center segments to toroidally shapethe tire carcass as illustrated in FIG. 11. When this is accomplished,the radially outer tip of the apex strip is moved back to its almostvertical position and the tire has been built in such a fashion that thecarcass, particularly at the bead core area is not overly stressed. Thishigh crown building drum 5, using the center segments, ensures that thecarcass has at least partially vertically extending ply portions priorto the ends being turned up. This more closely assimilates the finishedtire shape. Additionally, the movement radially outward of the centralsegments is about equal to the axial movement of the locked bead core oneach side. This ensures that the amount of axial tension is controlledto the tire carcass each and every time it is toroidally inflated,greatly improving the reliability of the finished product.

Next, the tire-building drum is further moved axially inward, and thetread belt and reinforcing structure is applied to the carcass and thenstitched. Next the shoulder clamp is actuated to the unlocked position,and the shoulder sections and the center section are moved radiallyinward to the start position of the drum. The green tire is thenremoved.

While certain representative embodiments and details have been shown forthe purpose of illustrating the invention, it will be apparent to thoseskilled in this art that various changes and modifications may be madetherein without departing from the spirit or scope of the invention.

1. A method of building a tire carcass on a tire building drumcomprising the steps of: applying one or more tire building componentsonto a rotating drum to form a cylindrically shaped unvulcanized tirecarcass having carcass ends; wherein said drum has a center section anda first and second shoulder section, said center section being radiallyexpandable, said center section further comprising center segmentshaving a first half and a second half, wherein the first half isconnected to a first ring and the second half is joined to a secondring, wherein said first and second rings are rotatably mounted withinthe first half and second half, respectively; wherein the first andsecond rings are joined together by one or more linkages for maintainingthe rotational synchronization of the first and second rings; placing afirst and second bead around the tire building components on the drum sothat the carcass ends of the tire carcass extend laterally between thebeads; radially expanding a first and second bead lock mechanism intoengagement with a first and second bead; moving the carcass locatedbetween the bead locks radially outward by radially expanding the centersection of the tire building drum while moving the pair of bead lockmechanisms axially inward and while rotating said first and second ringstogether within the center segments, and maintaining the synchronizationof the rotation of the rings by the one or more linkages.
 2. The methodof claim 1 further comprising the steps of turning up the tire carcassends and stitching the turnups to form a partially radially extendingturnup.
 3. The method of claim 1 further comprises inflating through acentral portion of the drum to toroidally shape the carcass.
 4. Themethod of claim 1 wherein the step of moving the carcass radiallyoutwardly between the bead locks includes moving the center segments adistance D, D being at least 20 mm.
 5. The method of claim 3 whereineach of the bead lock mechanisms moves a distance axially inward aboutequal to the radial movement distance of the center segments.
 6. Themethod of claim 1 wherein the carcass is mounted over a sleeve on thetire building drum, wherein the axial tension of the sleeve ismaintained when a portion of the tire building drum is radiallyexpanded.
 7. The method of claim 1 wherein the axial tension of thecarcass is maintained when a portion of the tire building drum isradially expanded.
 8. The method of claim 3 wherein each of the beadlock mechanisms moves a distance axially inward slightly less than theradial movement of the center segments.
 9. The method of claim 1 whereinthe first half and the second half are axially movable with respect toeach other so that the center section has an adjustable width, themethod further comprising the step of axially contracting the centersection of the tire building drum and then toroidally shaping thecarcass.
 10. The method of claim 1 wherein each of said shouldersections is independently movable relative to the other shoulder sectionin the radial direction and the axial direction and adjusting the firstand second beads to different diameters with respect to each other. 11.The method of claim 1 wherein the first and second bead lock mechanismsare actuated independently of each other.
 12. The method of claim 1wherein the first half and the second half each comprise pluralchambers, each of said chambers having a first substantially radiallyoriented end and a second substantially axially oriented end; eachchamber having an actuatable linkage disposed in said chamber, saidlinkage having a first end in communication with an actuator and asecond end connected to one of said first and second halves, whereinactuation of the linkages from the axially oriented end to the radiallyoriented end of the chamber causes the expansion of the center section.